Fever of unknown origin (FUO) is an entity caused by more than 200 diseases. Haematologic neoplasms are the most common malignant cause of FUO. Fever as a first symptom of colonic tumour pathology, both benign and malignant, is a rare form of presentation. Our work is a descriptive study of a series of 23 patients with colonic tumoral pathology who presented with fever of unknown origin. The mean age was 67.6 years; 56.5% of patients were men and 43.5% were women. Primary malignant neoplasia was the most common diagnosis. Blood cultures were positive in 45% of the samples. Coagulase-negative staphylococci were the most common cause of bacteraemia. Nine of 10 faecal occult blood tests performed were positive. Fever secondary to colon neoplasms, both benign and malignant, usually presents with a bacteraemic pattern, with positive results for blood-culture tests in a high percentage of cases.